The invention relates to transmission path delay determination.
In electronic devices, such as base stations of radio systems, signals are transmitted between different electronic circuits. The circuits may form what is known as a driver/receiver pair, in which the driver transmits a data signal, such as a clock signal, to the receiver.
The transmission media may be, for example, a wire printed on a circuit board, a cable, connectors, or the like, placed between and coupling the driver and the receiver, and will always delay propagation of the signal. An electronic device may comprise a plural number of driver/receiver pairs, and the elements of the pairs may appear in diverse parts of the electronic device. For example, a base station may comprise a driver, which may be a transceiver, and a receiver, which may be a frequency amplifier, frequency synthesizer or masthead amplifier connected to the transceiver.
An electronic device may comprise a plurality of driver/receiver pairs providing the same functionality, the proper functioning of the device requiring the signal, such as a clock signal, transmitted by the drivers to be received simultaneously at each respective receiver. A problem arises from the transmission media used between the different driver/receiver pairs because the delay caused by the media may vary according to each pair. This is due to variations in the physical length of the wire and the electric properties of the wire and the connectors.
Different solutions have been proposed to this problem. The electronic device may be designed to tolerate delays of a specific length. This, however, complicates the planning of the device and, in addition, may require an additional buffer memory. Another solution is to calculate the lengths of the delays and provide the device with a fixed signal timing adjustment for balancing the delays. This solution is not, however, feasible for base stations, where the length of the transmission media between the transceiver and the masthead amplifier may vary from dozens of centimeters to dozens of meters, for example. In other words, the length of the transmission media varies according to the product and/or application environment. Similarly, the electric properties of the transmission media may vary depending on the supplier.
U.S. Pat. No. 5,570,054 discloses a solution in which double wiring is used between the driver/receiver pair for supplying the signal from the driver to the receiver and for receiving feedback of the phase difference from the receiver to the driver. The feedback is used for correcting the signal phase. The solution requires double wiring and, since it is a continuous operation, it increases the power consumption of the device.
The present invention seeks to provide an improved method and apparatus. According to at least one embodiment of the present invention, a method is provided in which a transmission path delay is determined based on a measured time duration necessary for receiving a reflection of a test signal, a line impedance termination between a first and second electronic circuit is reconfigured and timing of a payload signal is adjusted based on the transmission path delay.
According to at least one embodiment of the present invention, a system is provided means for measuring a time duration necessary for receiving a reflection of a test signal, means for determining a transmission path delay as half of the measured time duration, means for reconfiguring a line impedance termination circuit after the transmission path delay has been determined; and means for adjusting the timing of the transmission of the payload signal on the basis of the transmission path delay.
According to at least one embodiment of the present invention, a system is provided including a first electronic circuit that is configured to receive a reflection of a test signal from a second electronic circuit, measure a time duration necessary for receiving the reflection of the test signal, determine a transmission path delay as half of the measured time duration, and adjust the timing of the transmission of a payload signal based on the transmission path delay.